Pump

ABSTRACT

A pump includes a cylinder formed with a plunger chamber, a low-pressure portion, to which low-pressure fuel is supplied, a plunger reciprocating in the cylinder to pressurize fluid in the chamber, which is drawn from the portion, and a magnet valve having a valve body. A low-pressure passage communicates between the chamber and the portion. The magnet valve blocks the passage with the valve body when energized, to control timing, with which fluid in the chamber starts to be pressurized by the plunger. Dynamic pressure of fluid flowing from the chamber into the passage is applied to the valve body in a direction in which the valve body closes the passage. The valve body includes an inclined surface at a portion of the valve body, to which the dynamic pressure is applied. The surface is nonparallel to a plane, which is perpendicular to a displacement direction of the valve body.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2006-287520 filed on Oct. 23, 2006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a pump.

2. Description of Related Art

In a conventional pump, timing, with which fuel starts to be pressurized by a plunger, is controlled by a valve body blocking a low-pressure passage communicating between a plunger chamber and a low-pressure portion upon energization. The conventional pump is used for a fuel injection apparatus for injecting fuel into a compression-ignition engine. The conventional pump is configured such that dynamic pressure of fuel flowing from the plunger chamber toward the low-pressure passage is applied to the valve body in a direction in which the valve body is closed (e.g., JP64-73166A).

In recent years, however, there has been an increasing demand for high fuel injection pressure in the compression-ignition engine. Accordingly, fuel leakage from an injector increases, so that a necessary discharge amount is increased, thereby increasing a cam lift in a fuel injection pump.

The large cam lift results in a high fuel feed rate, and high-speed rotation of a cam shaft brings about high dynamic pressure of fuel in the plunger chamber. The valve body of a magnet valve is easily closed by itself due to the dynamic pressure. When the valve body is closed by itself, the timing, with which fuel starts to be pressurized by the plunger, becomes earlier than target timing, and consequently the discharge amount of the pump cannot be controlled.

SUMMARY OF THE INVENTION

The present invention addresses the above disadvantages. Thus, in a pump configured such that dynamic pressure of fluid flowing from a plunger chamber toward a low-pressure passage is applied to a valve body of a magnet valve in a direction in which the valve body closes the low-pressure passage, it is an objective of the present invention to prevent the valve body from closing the low-pressure passage by itself due to the dynamic pressure. The magnet valve of the pump controls timing, with which fluid starts to be pressurized by a plunger, by blocking the low-pressure passage communicating between the plunger chamber and a low-pressure portion with the valve body upon energization.

To achieve the objective of the present invention, there is provided a pump including a cylinder, a low-pressure portion, a plunger, and a magnet valve. The cylinder is formed with a plunger chamber. Low-pressure fuel is supplied to the low-pressure portion. A low-pressure passage communicates between the plunger chamber and the low-pressure portion. The plunger reciprocates in the cylinder to pressurize fluid in the plunger chamber, which is drawn from the low-pressure portion. The magnet valve has a valve body. The magnet valve blocks the low-pressure passage with the valve body when energized, to control timing, with which fluid in the plunger chamber starts to be pressurized by the plunger. Dynamic pressure of fluid flowing from the plunger chamber into the low-pressure passage is applied to the valve body in a direction in which the valve body closes the low-pressure passage. The valve body includes an inclined surface at a portion of the valve body, to which the dynamic pressure is applied. The inclined surface is nonparallel to a plane, which is perpendicular to a displacement direction of the valve body.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which:

FIG. 1 is a sectional view illustrating a pump according to a first embodiment of the present invention;

FIG. 2 is a sectional view illustrating a magnet valve in FIG. 1;

FIG. 3 is a schematic view illustrating a substantial portion of a valve body in a pump according to a second embodiment of the present invention;

FIG. 4 is a schematic view illustrating a substantial portion of a valve body in a pump according to a third embodiment of the present invention;

FIG. 5 is a schematic view illustrating a substantial portion of a valve body in a pump according to a fourth embodiment of the present invention; and

FIG. 6 is a schematic view illustrating a substantial portion of a valve body in a pump according to a fifth embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION First Embodiment

A first embodiment of the present invention is described below with reference to FIGS. 1, 2.

A pump according to the first embodiment is used as a fuel-supply pump, which supplies high-pressure fuel to a common rail storing high-pressure fuel in a fuel injection apparatus for injecting fuel into a compression-ignition engine.

As shown in FIGS. 1, 2, a pump housing 10 has a cam chamber 10 a, a cylindrical slider insertion hole 10 b, and a cylindrical cylinder insertion hole 10 c. The cam chamber 10 a is located on a lower end side of the pump housing 10. The slider insertion hole 10 b extends in a direction from the cam chamber 10 a toward an upper portion of the pump housing 10. The cylinder insertion hole 10 c extends in a direction from the slider insertion hole 10 b to an upper end surface of the pump housing 10.

A cam shaft 11, which is driven by the compression-ignition engine (not shown: hereafter referred to as an internal combustion engine), is disposed in the cam chamber 10 a. The cam shaft 11 having a cam 12 is rotatably held by the pump housing 10.

A cylinder 13 is fitted into the cylinder insertion hole 10 c in such a manner that the cylinder 13 blocks the cylinder insertion hole 10 c. The cylinder 13 has a cylindrical insertion hole 13 a, and a cylindrical plunger 14 is reciprocatably inserted into the insertion hole 13 a. A plunger chamber 15 is defined by an upper end surface of the plunger 14 and an inner circumferential surface of the cylinder 13.

A seat 14 a is connected to a lower end portion of the plunger 14, and is pressed on a slider 17 by a spring 16. The slider 17 is cylindrically formed, and is reciprocatably inserted into the slider insertion hole 10 b. A cam roller 18 is rotatably joined to the slider 17, and is in contact with the cam 12. When the cam 12 is rotated by rotation of the cam shaft 11, the plunger 14 is driven to reciprocate together with the seat 14 a, the slider 17, and the cam roller 18.

A fuel pool 19 serving as a low-pressure portion is formed between the cylinder 13 and the pump housing 10. Low-pressure fuel discharged from a low-pressure supply pump (not shown) is supplied to the fuel pool 19 through a low-pressure fuel pipe (not shown). The fuel pool 19 communicates with the plunger chamber 15 via a low-pressure communicating passage 13 b formed in the cylinder 13 and a low-pressure passage 31 a formed in a magnet valve 30, which is described in greater detail hereinafter.

A high-pressure communicating passage 13 c, which is in constant communication with the plunger chamber 15, is formed in the cylinder 13. The plunger chamber 15 is connected to a common rail (not shown) through the high-pressure communicating passage 13 c, a delivery valve 20, and a high-pressure fuel pipe (not shown) in this order. The high-pressure communicating passage 13 c and the high-pressure fuel pipe constitute a high-pressure fuel supply route.

The delivery valve 20 is joined to the cylinder 13 on a downstream side of the high-pressure communicating passage 13 c. The delivery valve 20 includes a valve body 20 a and a spring 20 b. The valve body 20 a opens or closes the high-pressure fuel supply route. The spring 20 b urges the valve body 20 a in a direction in which the valve body 20 a is closed. Fuel pressurized in the plunger chamber 15 displaces the valve body 20 a in a direction in which the valve body 20 a is opened, against urging force of the spring 20 b, and is force fed into the common rail.

The magnet valve 30 is disposed in opposition to the upper end surface of the plunger 14, and is threaded and fixed to the cylinder 13 to block the plunger chamber 15.

The magnet valve 30 has a body 31, which includes the low-pressure passage 31 a and a seat portion 31 b. One end portion of the low-pressure passage 31 a communicates with the plunger chamber 15, and the other end portion communicates with the low-pressure communicating passage 13 b. The seat portion 31 b is formed in the low-pressure passage 31 a.

The magnet valve 30 has a solenoid 32, an armature 33, a spring 34, a valve body 35, and a stopper 36. The solenoid 32 generates attraction force upon energization. The armature 33 is attracted by the solenoid 32. The spring 34 urges the armature 33 in an opposite direction from a direction in which the armature 33 is attracted. The valve body 35 is displaced integrally with the armature 33 and closes or opens the low-pressure passage 31 a by engaging or disengaging from the seat portion 31 b, respectively. The stopper 36 restricts displacement of the valve body 35 when the valve body 35 is opened.

The stopper 36 is held between the magnet valve 30 and the cylinder 13, and has a plurality of communicating holes 36 a, which communicate between the low-pressure passage 31 a and the plunger chamber 15.

Dynamic pressure (hereinafter referred to as overflowing dynamic pressure) of fuel flowing from the plunger chamber 15 to the low-pressure passage 31 a is applied to the valve body 35 in a direction in which the valve body 35 is closed. An inclined surface 35 a is formed on a surface of the valve body 35, to which the overflowing dynamic pressure is applied. The inclined surface 35 a is not parallel to a plane, which is perpendicular to a displacement direction X of the valve body 35 (which, in the present example, coincides with a direction in which the overflowing dynamic pressure is applied).

More specifically, the inclined surface 35 a is a tapered surface having a diameter that increases at a constant rate in the direction in which the overflowing dynamic pressure is applied. That is, a portion of the valve body 35 including the inclined surface 35 a has a truncated cone shape. In other words, the inclined surface 35 a has, when viewed from a direction perpendicular to the displacement direction X of the valve body 35, a linear appearance. The inclined surface 35 a of the valve body 35 has a tapered shape because it is easily formed. The inclined surface 35 a is inclined by, for example, 45 degrees with respect to the displacement direction X.

The valve body 35 has a seat surface 35 b, which engages or disengages from the seat portion 31 b of the body 31.

Workings of the pump having the above-described configuration are described below. When the solenoid 32 of the magnet valve 30 is not energized, the valve body 35 is displaced to a position in which the valve body 35 is opened by urging force of the spring 34. That is, the seat surface 35 b of the valve body 35 is disengaged from the seat portion 31 b, and thereby the low-pressure passage 31 a is opened.

When the plunger 14 is displaced in a downward direction in FIG. 1 with the low-pressure passage 31 a being opened, low-pressure fuel discharged from the low-pressure supply pump is supplied to the plunger chamber 15 through the fuel pool 19, the low-pressure communicating passage 13 b, and the low-pressure passage 31 a in this order.

Next, when the plunger 14 starts to be displaced in an upward direction in FIG. 1, the plunger 14 moves to pressurize fuel in the plunger chamber 15. However, when the plunger 14 starts to be displaced upward, since the magnet valve 30 is not energized so that the low-pressure passage 31 a is opened, fuel in the plunger chamber 15 overflows into the fuel pool 19 through the low-pressure passage 31 a and the low-pressure communicating passage 13 b in this order, and thereby is not pressurized.

When the magnet valve 30 is energized while fuel in the plunger chamber 15 is overflowing, the armature 33 and the valve body 35 are attracted, against the spring 34, so that the seat surface 35 b engages the seat portion 31 b to block the low-pressure passage 31 a. Accordingly, fuel in the plunger chamber 15 stops overflowing into the fuel pool 19, and starts to be pressurized by the plunger 14. The delivery valve 20 is opened due to pressure of fuel in the plunger chamber 15, so that fuel is force fed into the common rail.

In the first embodiment, the inclined surface 35 a is formed on the surface of the valve body 35, to which the overflowing dynamic pressure is applied. Accordingly, when the overflowing dynamic pressure is applied to the valve body 35, the inclined surface 35 a generates components of force in the direction perpendicular to the displacement direction X of the valve body 35, to decrease force applied in a direction in which the valve body 35 is closed by itself. As a result, the closing of the valve body 35 by itself due to the overflowing dynamic pressure is restricted, so that a fuel discharge amount of the pump is accurately controlled.

Second Embodiment

A second embodiment of the present invention is described below with reference to FIG. 3.

The inclined surface 35 a of the valve body 35 in the first embodiment has, when viewed from the direction perpendicular to the displacement direction X of the valve body 35, a linear appearance. However, an inclined surface 35 a of a valve body 35 in the second embodiment has, when viewed from the direction perpendicular to the displacement direction X, an arc-like appearance. More specifically, a diameter of the inclined surface 35 a gradually increases in the direction in which the overflowing dynamic pressure is applied, and then sharply increases. In other words, the diameter of the inclined surface 35 a gradually increases on its side near the plunger chamber 15, and sharply increases on its side distant from the plunger chamber 15.

Third Embodiment

A third embodiment of the present invention is described below with reference to FIG. 4.

The inclined surface 35 a in the first embodiment has, when viewed from the direction perpendicular to the displacement direction X, a linear appearance. However, an inclined surface 35 a of a valve body 35 in the third embodiment has, when viewed from the direction perpendicular to the displacement direction X, an arc-like appearance. More specifically, a diameter of the inclined surface 35 a sharply increases in the direction in which the overflowing dynamic pressure is applied, and then gradually increases. In other words, the diameter of the inclined surface 35 a sharply increases on its side near the plunger chamber 15, and gradually increases on its side distant from the plunger chamber 15.

Fourth Embodiment

A fourth embodiment of the present invention is described below with reference to FIG. 5.

The inclined surface 35 a in the first embodiment has, when viewed from the direction perpendicular to the displacement direction X, a linear appearance. However, an inclined surface 35 a of a valve body 35 in the fourth embodiment has, when viewed from the direction perpendicular to the displacement direction X, an arc-like appearance. More specifically, the inclined surface 35 a has a hemispherical shape.

Fifth Embodiment

A fifth embodiment of the present invention is described below with reference to FIG. 6.

The inclined surface 35 a of the valve body 35 in the first embodiment is formed in a tapered shape. However, a valve body 35 in the fifth embodiment has a cylindrical portion 35 c, and an inclined surface 35 a is formed such that a portion of the cylindrical portion 35 c, to which the overflowing dynamic pressure is applied, is trimmed diagonally with respect to the displacement direction X.

Other Embodiments

In the above-described embodiments, the present invention is applied to the fuel-supply pump in the fuel injection apparatus for the internal combustion engine. Nevertheless, the present invention may be broadly applied to a pump, which draws and discharges fluid.

Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. 

1. A pump comprising: a cylinder formed with a plunger chamber; a low-pressure portion, to which low-pressure fuel is supplied, wherein a low-pressure passage communicates between the plunger chamber and the low-pressure portion; a plunger that reciprocates in the cylinder to pressurize fluid in the plunger chamber which is drawn from the low-pressure portion; and a magnet valve having a valve body, wherein: the magnet valve blocks the low-pressure passage with the valve body when energized, to control timing, with which fluid in the plunger chamber starts to be pressurized by the plunger; dynamic pressure of fluid flowing from the plunger chamber into the low-pressure passage is applied to the valve body in a direction in which the valve body closes the low-pressure passage; the valve body includes an inclined surface at a portion of the valve body, to which the dynamic pressure is applied; and the inclined surface is nonparallel to a plane, which is perpendicular to a displacement direction of the valve body.
 2. The pump according to claim 1, wherein the inclined surface is formed in a tapered shape.
 3. The pump according to claim 1, wherein the inclined surface has, when viewed from a direction perpendicular to the displacement direction of the valve body, an arc-like appearance. 